Just after writing that post I've thought it may be the antivirus, and I was right. It seems Windows Defender takes longer to check Spectaculator than any other executable file, so I've added it to exclusions and now it starts fast again.

Knowing which antivirus in particular presents this behaviour is useful.

Having executable files as exclusions is always bad, since specific virus may target those files, if they are known to be typically excluded from antivirus software.

In my opinion Antivirus Exclusions, should always be protected with some kind of CRC and date change validation, so that if the executable file somehow changes, the exclusions should be invalidated, in the sense that the file now needs to be checked again, and the user should be warned about it.

I'm not sure if this kind of check is supported on any of the Antivirus softwares that I know.

It would probably be over kill. For something to modify the Spectaculator executable when excluded, it would have to be running itself and presumably not excluded from scanning. If a scanner was going to pick it up, it's a likely to do it then as it would be if scanning Spectaculator itself.

I've been having a lot of Windows lagginess lately, and I think Spectaculator (8.0.0.3092) might be causing it. I have my assembler launch Spectaculator at the end of assembly, and I instinctively close it again most of the time. After Spectaculator has been launched and exited about 50 times, everything in Windows gets horribly laggy - even application menus (in every app) take about 5 seconds to display. Even when my both my assembler and Spectaculator aren't running. Only a reboot will fix it. Sometimes I have to reboot two or three times in an evening. Kernel object resource leaks? I'm using TR-DOS in this scenario, so maybe it's something to do with that module. I need to investigate further.

I'm not sure if this kind of check is supported on any of the Antivirus softwares that I know.

My antivirus WebRoot actually does this, for both virus scanning and firewall outgoing connection checking. It's actually kind of annoying, because some of the software I build triggers this over and over and again, and I can't seem to set permanent exclusions.

WebRoot doesn't seem to be a particularly well-known or community-rated package, but we have an existing family subscription, and I installed it after I got some malware that Windows Defender failed to stop, and I've since found it to be very competent.